In plain English
FAR 52.249-12, Termination (Personal Services), is a contract clause prescribed at FAR 49.505(a), most recently dated Apr 1984. The complete official text is reproduced below, verbatim, from GSA's published FAR source files.
Its text contains no sentence requiring insertion into subcontracts; see the flowdown section below for what that does and does not mean.
Does it flow down to subcontracts?
No flowdown mandate found in the clause text
We scanned the full clause text and found no sentence directing the contractor to insert this clause into subcontracts. That is a statement about the text, not legal advice: a prime contractor may still flow terms down contractually, an agency supplement (DFARS, VAAR, …) may add requirements, and clauses listed below (if any) may order this clause into subcontracts from the outside.
Where it's prescribed
As prescribed in 49.505(a), insert the following clause in solicitations and contracts for personal services (see part 37 ):
Prescribing reference: FAR 49.505(a).
The official text, verbatim
As prescribed in 49.505(a), insert the following clause in solicitations and contracts for personal services (see part 37 ):
Termination (Personal Services) (Apr 1984)
The Government may terminate this contract at any time upon at least 15 days’ written notice by the Contracting Officer to the Contractor. The Contractor, with the written consent of the Contracting Officer, may terminate this contract upon at least 15 days’ written notice to the Contracting Officer.
(End of clause)